Geological Field Observations Research Articles

Geochemistry and origin of listwaenites within the Northern Branch of Neo-Tethyan ophiolites, Turkey

The study presents geological field observations, petrographic characteristics and bulk rock geochemical data of listwaenitic occurrences related to Jurassic–Cretaceous IAESZ ophiolites of the northern part of Turkey. Listwaenites of the Jurassic–Cretaceous Eldivan ophiolite and the Cretaceous Dağküplü ophiolite occur as mineralised or non-mineralised blocks and/or veins associated with serpentinised peridotites and ophiolitic mélanges along major thrust zones within the Izmir–Ankara–Erzincan Suture Zone (IAESZ) of the Northern Branch of the Neo-Tethys, Turkey. The silica–carbonate listwaenites (Type I) consist mainly of dolomite and minor calcite with quartz and minor phyllosilicates (chlorite, mica), serpentine and hematite. They are formed by circulation of meteoric hydrothermal fluids, along major décollement faults and thrust faults during the emplacement of serpentinised peridotites. The Kaymaz listwaenites (Type II) are composed mainly of fine-grained microcrystalline quartz with negligible dolomite, calcite, magnesite, serpentine and Fe-hydroxides. They display hard resistant masses, and are adjacent to the Eocene granitic bodies. Listwaenites are gentically related to the serpentinised peridotites, while the mineralisation appears to be related to the granite-related hydrothermal fluids.

Lithostructural Mapping Using Landsat OLI images and Field Investigations in the Oumjrane–Boukerzia Mining District, Eastern Anti-Atlas, Morocco

The application of remote sensing is considered to be highly efficient in the field of geology, particularly for mapping and discrimination between lithological units, as well as the identification of different surface minerals which enable the acquisition of all the optical and radar data needed to obtain more reliable and particular information, especially in inaccessible areas. Landsat 8 (Operational Land Imager) image bands, which include color compositions 7, 4, and 1, band ratios 7/5, 4/2, 3/1, and 6/3, 6/1, 5/2, Principal Component Analyses PC1, PC4, and PC3, and directional filtering at 0° (NS), 45° (NE–SW), and 90° (EW), were used to analyze the spectral characteristics of the lithological units of the study area and delineate the alteration zones which may contain significant concentrations of base metals. Combined with geological field observations, these data were integrated and analyzed in a geographic information system to establish a multi-criteria characterization of mineralized zones. Hence, the use of remote sensing contributed to the improvement and updating of available geological maps of the Oumjrane–Boukerzia area. Lineament extraction allowed for performed analyses of the structural elements that play a crucial role in the mineral distribution in the study area. Several of the targeted areas were examined in the field by selective sampling. Consequently, the results helped identify new mineralized zones with important mining potential which could be evaluated in the future through detailed geophysical and geochemical work.

Investigation of the main reservoir of the Tulehu geothermal system (Indonesia) using 3-D inversion of MT data

Tulehu geothermal prospect area is located in Maluku Province, Indonesia. The existence of the geothermal system in this area is recognized by the appearance of hot springs on the western side of Mt Eriwakang and the northern side of Mt. Huwe. Most of these hot springs occur along inferred geological structures. The geological conditions of this area are dominated by Quaternary volcanic rocks, limestone, alluvium, and metamorphic rocks. Several authors have conducted several studies to propose various geothermal conceptual models, from structurally controlled to volcanic-hosted geothermal systems. However, the geoscientific data supporting the hypotheses are not comprehensive yet. There are still gaps in the data coverage as well as in the interpretation of geological, geochemical, and geophysical data, so a comprehensive study should be done before deciding on further stages. Therefore, this paper proposes a new conceptual model of the Tulehu geothermal area by reducing the existing data gap. Interpretation of remote sensing data, geological field observations, age dating analysis, reanalysis of geochemical data, and additional MT data covering Mt. Eriwakang are conducted to reconstruct the conceptual model. Graben-like structures are identified based on the geological data where the product of Mt. Eriwakang is in the middle. Based on the age dating data, the product of Mt. Eriwakang erupted in the Quaternary time (413±6 kA), so it is still quite potential as a heat source. This indication is also supported by the trend of Cl, HCO3, and SiO2, which describe the possible flow from Mt. Eriwakang to the surrounding hot springs. Based on the Na-K-Mg and Silica geothermometers, the reservoir temperature is estimated at 210-240 °C. A three-dimensional (3-D) MT inversion was applied to all the existing and new MT data to obtain a 3-D subsurface resistivity model. The oceanic bathymetry data was also incorporated to mitigate the possible coastal effect from the surrounding seawater to the MT data. The new 3-D MT inversion results show a good agreement with the geological and geochemical indications. The updome-shaped pattern of the subsurface resistivity distribution beneath Mt. Eriwakang supports the geological and geochemical data analysis results concerning the indications of the prospects area around Mt. Eriwakang. These interpretations can strengthen the recommendation to focus on the area around Mt. Eriwakang for further development.

Characteristics of Mengger Formation’s volcaniclastic in Cisaat River, Brebes, Central Java, Indonesia

The Cisaat River in Brebes Regency, Central Java, is one of the sites on Java Island where vertebrate fossils were found. Mengger Formation, composed of volcaniclastics material such as tuff and pumice fragments, contains these fossils. The presence of vertebrate fossils along with volcanic deposits has remained unclear of its deposition history. This research characterizes the volcaniclastic rocks in Mengger Formation based on geological field observation and petrography analysis. The study aims to identify and distinguish its primary and secondary volcaniclastic depositional processes. The measured stratigraphic sections reveal that the formation has 7 lithofacies from older to younger, namely grain-supported conglomerate, sandstone, siltstone, sandy mudstone, matrix-supported conglomerate, tuffaceous sandstone, and tuffaceous conglomerate. The primary volcaniclastic materials comprise pumice clast, plagioclase, pyroxene, hornblende, quartz, biotite, lithic fragments, and volcanic glass. In contrast, secondary volcaniclastic or epiclastic-sedimentary materials contain lithic fragments, quartz, plagioclase, pumice clast, and clay matrix. The origin of the resedimented volcaniclastic material was probably derived from a large volume of ignimbrite near the volcano. From the deposit and measurement section, it can be concluded that the type of the Mengger volcaniclastic.

Late Archean–Paleoproterozoic plate tectonics along the northern margin of the North China craton

AbstractThe North China craton of central Asia is a natural laboratory for investigating early Earth tectonic processes including subduction and large-scale horizontal crustal motions. However, it remains unclear how and when the North China craton formed from the amalgamation of several blocks and orogens including the Archean Western and Eastern blocks, the late Archean Central Orogenic Belt, and the Paleoproterozoic Northern Margin orogen. In this study, we integrated new and existing geological field observations, zircon and baddeleyite U-Pb geochronology, whole-rock geochemistry, and Sr-Nd-C-O isotope analyses along the northern margin of the North China craton to improve our understanding of its late Archean–Paleoproterozoic tectonic evolution. Observations show the Wuchuan ultramafic-mafic complex of the Northern Margin orogen contains a mixture of mylonite gneiss, serpentinized ultramafic blocks, and amphibolite pyroxenite xenoliths. Geochronology and geochemistry results suggest that the ca. 2.55–2.5 Ga development of the Wuchuan ultramafic-mafic complex was associated with subduction, which was followed by ca. 2.39 emplacement of lamprophyre dikes during continental rifting. Subsequent Paleoproterozoic subduction magmatism, continental collision, and post-orogenic rifting between the North China craton and southern margin of the Siberian craton are evidenced by ca. 2.0 Ga arc granitoids, ca. 1.87–1.85 Ga A-type, garnet-bearing granitoids and mafic dikes, and ca. 1.86 carbonatite. Ca. 2.0 Ga collision and ca. 1.87–1.85 Ga rifting were coincident with orogen-normal left-slip shear. Our findings show that the ca. 1.9 Ga North China-Siberia collision was a key event during the assembly of the Columbia supercontinent that occurred via modern plate-tectonic processes.

Geological mapping and mining prospecting in the Aouli inlier (Eastern Meseta, Morocco) based on remote sensing and geographic information systems (GIS)

Landsat 8 Oli, ASTER, and Sentinel 2A satellite images processing was used to map geological formations, lineaments and hydrothermal alteration minerals in the Aouli inlier, as a case study to illustrate the application of digital images processing and Geographic Information System (GIS) in geological mapping and mining prospecting. Principal Component Analysis (PCA) applied to the Landsat images allowed good lithological discrimination and contributed to the updating of available geological maps. The Automatic lineament extraction from Sentinel images revealed the main tectonic structures affecting Aouli inlier. The ratio bands (b5+b7)/b6 and the false color composite (b4/b6, b2/b1, b3/b2) allowed the hydrothermal alteration minerals mapping from Aster images. Combined with available geological data and field observations, the satellite derived data were integrated and analyzed in a GIS software to establish mining prospecting guides. The results showed that the anomaly zones are intimately linked to NNE –SSW and NW –SE oriented faults and to highly fractured areas developing argillic and Fe rich alterations. Verified via field survey, this approach was successfully applied to the Aouli inlier to rapidly target potential areas to be explored in the tactical phase. This provides a model for future prospecting efforts for similar mineral deposits in other areas.©2022 China Geology Editorial Office.

PECULIARITIES OF THE COMPOSITION AND THERMODYNAMIC CONDITIONS OF FORMATION OF ENDERBITES OF THE HAIVORONSKYI COMPLEX (SOUTH-WESTERN PART OF THE UKRAINIAN SHIELD)

Mineralogical and petrographic features of enderbites of the Haivoronskyi complex in the south-western part of the Ukrainian Shield (the valley of the Pivdennyi Buh River from the town of Haivoron to the village of Zavallia) were studied. The complex of research included field geological observations on outcrops and in quarries and laboratory petrographic, mineralogical and petrogeochemical studies. Such minerals as quartz, plagioclase (albite–oligoclase, andesine– bytownite), K-feldspar (microcline), rhombic (ferrosilite) and monoclinic (diopside, augite) pyroxenes, garnets, biotite, apatite, ilmenite, monazite, carbonates (calcite, dolomite) have been described. The temperature of mineral formation was calculated using garnet-biotite, garnetorthopyroxene and two-feldspar geothermometers according to the data of various authors using theoretical calculations and a graphic method. The thermodynamic conditions for the formation of enderbites during three stages were determined on the basis of the conducted research and literature data.

Proterozoic–Phanerozoic tectonic evolution of the Qilian Shan and Eastern Kunlun Range, northern Tibet

AbstractThe Proterozoic–Phanerozoic tectonic evolution of the Qilian Shan, Qaidam Basin, and Eastern Kunlun Range was key to the construction of the Asian continent, and understanding the paleogeography of these regions is critical to reconstructing the ancient oceanic domains of central Asia. This issue is particularly important regarding the paleogeography of the North China-Tarim continent and South China craton, which have experienced significant late Neoproterozoic rifting and Phanerozoic deformation. In this study, we integrated new and existing geologic field observations and geochronology across northern Tibet to examine the tectonic evolution of the Qilian-Qaidam-Kunlun continent and its relationships with the North China-Tarim continent to the north and South China craton to the south. Our results show that subduction and subsequent collision between the Tarim-North China, Qilian-Qaidam-Kunlun, and South China continents occurred in the early Neoproterozoic. Late Neoproterozoic rifting opened the North Qilian, South Qilian, and Paleo-Kunlun oceans. Opening of the South Qilian and Paleo-Kunlun oceans followed the trace of an early Neoproterozoic suture. The opening of the Paleo-Kunlun Ocean (ca. 600 Ma) occurred later than the opening of the North and South Qilian oceans (ca. 740–730 Ma). Closure of the North Qilian and South Qilian oceans occurred in the Early Silurian (ca. 440 Ma), whereas the final consumption of the Paleo-Kunlun Ocean occurred in the Devonian (ca. 360 Ma). Northward subduction of the Neo-Kunlun oceanic lithosphere initiated at ca. 270 Ma, followed by slab rollback beginning at ca. 225 Ma evidenced in the South Qilian Shan and at ca. 194 Ma evidenced in the Eastern Kunlun Range. This tectonic evolution is supported by spatial trends in the timing of magmatism and paleo-crustal thickness across the Qilian-Qaidam-Kunlun continent. Lastly, we suggest that two Greater North China and South China continents, located along the southern margin of Laurasia, were separated in the early Neoproterozoic along the future Kunlun-Qinling-Dabie suture.

Airborne/UAV Multisensor Surveys Enhance the Geological Mapping and 3D Model of a Pseudo-Skarn Deposit in Ploumanac’h, French Brittany

Taking advantage of a multi-sensor (multispectral and magnetic) drone survey, we address the detailed geological mapping and modeling of a mineralization in its geological environment. We stress that these high-resolution data allow us to bridge the gap between field observations and a regional aeromagnetic survey. On the one hand, the combination of multispectral imagery with field geological observations enhances detailed geological mapping. On the other hand, the combination of field magnetic susceptibility measurement and their use in detailed to regional magnetic modeling, constrained respectively by UAV-borne and airborne magnetic surveys, allows deriving a model of the mineralization consistent across the scales. This is demonstrated in a case study in a complex polyphased magmatic-metamorphic environment on the coast of French Brittany. The target area hosts a pseudo-skarn mineralization, exhibiting an outstanding magnetic anomaly. The combination of remotely sensed and field data allows deriving a realistic conceptual and geometrical model of the magnetic mineralization in its geological environment, tightly constrained by field observations and measurements.

Re-interpretation of distribution of Lautan Pasir caldera-forming eruption products, Bromo-Tengger Caldera Complex, East Java

We present the result of morphostratigraphic analysis and geological field observation to identify the distribution of scoria flow deposit related to the caldera-forming eruption of Lautan Pasir caldera as the youngest caldera in Bromo-Tengger caldera complex. Morphostratigraphic analysis derived from digital elevation model and volcanic stratigraphy shows that products of Lautan Pasir caldera-forming eruption(s) mainly distributed to the north filled up the Sapikerep valley, and further to the north formed Sukapura distal fan. While to the south, it filled the valley between Ijo and Old Semeru. Field observation in the deeply dissected part of Sapikerep valley found two massive pyroclastic flow deposits separated by lava flow. Above the lava flow is scoria rich pyroclastic flow deposit typical of Lautan Pasir caldera-forming eruptions. Below the lava flow is scoria poor pyroclastic deposit of older products, most likely, of Ngadisari caldera. The distribution of Ngadisari caldera-forming eruption products is very limited considering the following massive volcanism of Lautan Pasir caldera. This outcrop might provide the key information to further reconstruct the volcanism stage of Bromo-Tengger caldera complex

Teaching with digital geology in the high Arctic: opportunities and challenges

Abstract. The Covid-19 pandemic occurred at a time of major revolution in the geosciences – the era of digital geology. Digital outcrop models (DOMs) acquired from consumer drones, processed using user-friendly photogrammetric software and shared with the wider audience through online platforms are a cornerstone of this digital geological revolution. Integration of DOMs with other geoscientific data, such as geological maps, satellite imagery, terrain models, geophysical data and field observations, strengthens their application in both research and education. Teaching geology with digital tools advances students' learning experience by providing access to high-quality outcrops, enhancing visualization of 3D geological structures and improving data integration. Similarly, active use of DOMs to integrate new field observations will facilitate more effective fieldwork and quantitative research. From a student's perspective, georeferenced and scaled DOMs allow for an improved appreciation of scale and of 3D architecture, which is a major threshold concept in geoscientific education. DOMs allow us to bring geoscientists to the outcrops digitally, which is particularly important in view of the Covid-19 pandemic that restricts travel and thus direct access to outcrops. At the University Centre in Svalbard (UNIS), located at 78∘ N in Longyearbyen in Arctic Norway, DOMs are actively used even in non-pandemic years, as the summer field season is short and not overlapping with the Bachelor “Arctic Geology” course package held from January to June each year. In 2017, we at UNIS developed a new course (AG222 “Integrated Geological Methods: From Outcrop To Geomodel”) to encourage the use of emerging techniques like DOMs and data integration to solve authentic geoscientific challenges. In parallel, we have established the open-access Svalbox geoscientific portal, which forms the backbone of the AG222 course activities and provides easy access to a growing number of DOMs, 360∘ imagery, subsurface data and published geoscientific data from Svalbard. Considering the rapid onset of the Covid-19 pandemic, the Svalbox portal and the pre-Covid work on digital techniques in AG222 allowed us to rapidly adapt and fulfil at least some of the students' learning objectives during the pandemic. In this contribution, we provide an overview of the course development and share experiences from running the AG222 course and the Svalbox platform, both before and during the Covid-19 pandemic.

A new type of unconventional gas reservoir from the nodular limestones of the Middle Permian Maokou Formation in the south‐eastern Sichuan Basin, south‐west China

A set of nodular limestones was developed in the first member of the Middle Permian Maokou Formation (denoted as the Mao‐1 member) in the south‐eastern Sichuan Basin, south‐west China. Borehole coring has shown excellent signals of oil and gas from the Mao‐1 member carbonates, and many drilling wells have obtained industrial‐level gas flow. To assess the natural gas exploration potential of the Mao‐1 member in this area, sedimentary characteristics of drilling cores are described, and the formation mechanism of natural gas reservoir and its key controlling factors are also evaluated using data obtained from field geological survey, core observation, and laboratory experimental analysis. On this basis, the process of natural gas accumulation and evolution is examined. The results show that the Mao‐1 member nodular limestone comprises abundant marls and packstone to wackestone, and they were deposited in a lower part of the carbonate ramp setting. The marls exhibit rather high organic‐matter abundance and hydrocarbon generation capacity. Natural gas is mostly enriched in the marls developed talc diagenetic shrinkage pores and a certain number of organic‐matter pores, and their reservoir properties are much better than that of packstone‐wackestone. The natural gas in the Mao‐1 member is mainly self‐generated oil pyrolysis gas. The gas reservoir is characterized by the co‐existence of source rocks and reservoir, a lithology‐controlled reservoir, and a structure‐fracture‐controlled enrichment mechanism. Organic‐matter‐rich marl constitutes the material basis for natural gas accumulation. Talc diagenetic shrinkage pores provide storage space for natural gas. Preservation conditions are the key to natural gas accumulation, and natural fractures are beneficial to high gas production. The gas reservoir is characterized by early intraformational enrichment and late interformational adjustment. The finding of the nodular limestone gas reservoir of the Mao‐1 member provides new insights into unconventional gas exploration in the Sichuan Basin, and shows great potential for increasing natural gas reserves and production in China.

GEOTHERMAL POTENTIAL ON SUMATRA FAULT SYSTEM TO SUSTAINABLE GEOTOURISM IN WEST SUMATRA

Sumatra Island is an island that is traversed an active ring of fire at Barisan Range which is related to the active Sumatra fault system and geothermal manifestations. It is associated with geothermal manifestations in Cubadak, Talu, Bonjol, and Rimbo Panti, Pasaman Regency, and West Pasaman Regency, West Sumatra Province, as an indication of a geothermal system connected to the Sumatra Fault System from the Sianok Segment and the Talamau Volcano Complex. Sustainable geotourism has become effective for sustainable development of geotourism, the geothermal energy direct utilization. The purpose of this study is to provide sustainable geotourism from geothermal potential in the fault system, taking into account aspects of village geotourism, ecotourism, ecoculture, and education. The methodology used in this study is to collect data on geothermal manifestations from regional geological maps and field observations in geothermal manifestation areas by considering sustainable geotourism. A simple model of sustainable geotourism is made. Study results indicate several locations of potential geothermal manifestations to be used as sustainable geotourism associated with the Sumatra Fault System and the Talamau Volcano Complex.

Activity-educational aspects of geological excursions

The purpose of this article is to discuss the educational tour as a form of educational process in the activity-the educational aspect of the geological excursion in the study of rock outcrops career «Borok» of Novosibirsk as a geological object of interest for educational tours and training-practical work. To write the article, we used methods of comparative analysis, generalization, field geological observations, sampling, cross-section sketches, descriptions of outcrops, including working with a mountain compass and methods of conducting a training geological-geographical and geoecological route, drawing up a map of the territory, laboratory studies of rocks. The absolute advantage of the Borok quarry is its location, as well as optimal conditions for a thorough inspection and description of rock outcrops. Branched dikes and veins are visible in the walls of the quarry, as well as the overlap of igneous Paleozoic rocks with sedimentary later deposits. Dumps of various Intrusive igneous, dike rocks and pegmatites, hydrothermal veins with ore minerals are of educational interest during excursions. The Borok quarry cooperates with schools, colleges, and Universities in Novosibirsk and is a platform for educational excursions to the production site and a place for training practices, as well as a venue for educational Olympiads in Geology and Geoecology. On the example of one of the production facilities of the city of Novosibirsk - the stone quarry «Borok», the possibilities of organizing and conducting geological excursions in order to study the geological structure of the territory, consolidate theoretical geological and geoecological knowledge, acquire skills in educational and practical work and analyze the results obtained are demonstrated.

Hydrogeophysical Characterization in a Volcanic Context From Local to Regional Scales Combining Airborne Electromagnetism and Magnetism

AbstractIn volcanic islands, a crucial step in managing watershed water resources is the characterization of groundwater aquifers from local to regional scales. Airborne geophysical data provide high‐resolution images down to hundreds of meters below the surface, over large areas. Yet, the production of an accurate interpretation of regional geophysical imagery may be time consuming or limited by the low density of geological and hydrological field observations. Here, we propose an approach combining airborne electromagnetic and magnetic data in order to reduce geophysical ambiguities and provide a multiscale hydrogeophysical characterization of Piton des Neiges volcano (Réunion Island). With limited calibration data, this methodology produces a geological model more accurate than using airborne electromagnetic data alone. Through the continuous coverage of both methods, we demonstrate the influence of volcanic unit geometries on groundwater flows within the critical zone and we highlight major structures impacting groundwater flows at both local and regional scales.

Geochemical anomaly definition using multifractal modeling, validated by geological field observations: Siah Jangal area, SE Iran

Recognition of geochemical anomalies is a pivotal assignment in exploration projects. This study aims to delineate different AuCu geochemical anomalies using number-size (N-S) and concentration-area (C-A) multifractal models in the Siah Jangal area, SE Iran. In this research, lithogeochemical datasets were applied for the exploration of Au and Cu. A comparison between geochemical anomaly maps based on the N-S and C-A fractal models shows the N-S fractal modeling is a powerful tool for separation of weak elemental geochemical anomalies in all of sampling zones. Based on a comparison between the results of these two methods and field studies, the geochemical anomaly zones, defined by the N-S fractal model, are more accurate than those recognized by the C-A fractal model. The obtained results of the N-S and C-A fractal models have been interpreted with the extensive set of information including structural interpretation, geological and alteration data. Au and Cu mineralization in the Siah Jangal area are hosted mainly by Oligocene-Miocene sub-volcanic rocks, especially strongly altered porphyric quartz diorite, hornblende diorite and diorite. Moreover, the positive dependence between various alteration zones and high concentrations of Au and Cu proves that strongly anomalous areas are correlated with these alteration zones. High grade Au (> 1000 ppb) and Cu (>150 ppm) are associated with the altered sub-volcanic rocks in the northern, eastern, and SW parts of the study area. Therewith, the strong anomaly populations are mostly occurred within the fault and fracture systems in the study area. This is a promising signal because quartz-sulfide veins and veinlets are associated with such structures.

Focused methane migration formed pipe structures in permeable sandstones: Insights from uncrewed aerial vehicle‐based digital outcrop analysis in Varna, Bulgaria

AbstractFocused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas.

Application of geoelectrical methods for identification of soil layer

Landslide is a geological event caused by the movement of rock or land mass that can be defined as the displacement of slope-forming material, which is the original rock as well as the other material that is moving with the gravity. The factors that influence landslides are soil layer, slip surface and saturated soil. Mapping or determining the landslide area is done by identifying several parameters that can trigger landslide. The geophysical method that can be used to analyse soil layer is resistance type of geoelectrical. Variations of each rock or soil layer resistance below the measuring point can be obtained from the measurements of current and potential differences. The research site is located East Aceh district, Indonesia. Geoelectrical measurements using Wenner-Schlumberger electrode configuration. Based on geological information, field observation and geophysical measuring results, the area is dominated by clay, sand and gravel material. Lithology of clay dominates the underside of the surface (until the depth of ± 30 meters. water that is held in sand lithology causes saturation of the sand. this is because there is a layer of clay under the sand which has low permeability or even impermeable properties. Saturated sand lithology can lead to contact between particles and has the potential to weaken it, causing soil movement.

The architecture of the Eopaleozoic Cococi Basin, northeastern Brazil: 2D geological modelling from magnetic and gravimetric data

Cococi Basin is a small Eopaleozoic syneclise that is overlying basement rocks of the Neoproterozoic Central Ceará Domain of the Borborema Province, northeastern Brazil. Its origin is associated with the final stages of the Brasiliano orogenic cycle (600 My). The Basin classified as rift type has its basement constituted by rocks of the Canindé Unit and the crosshead complex and delimited by Senador Pompeu and Tauá shear zones. Three geophysical cross-sections were created using aero-magnetometric and field gravimetric data, aiming to outline the litho-structural underground features of the Basin. We have used the following methods for processing and interpreting geophysical data: minimum curvature, analytic signal amplitude, Euler deconvolution, and 2D modeling. The obtained depth solutions were interpreted and combined with geological data to generate geological models featuring the limits and depth of the Basin, its internal main structures, and its lithological variations. The developed geophysical-based geological modeling unravels the yet unknown geological features of the Cococi Basin, which corroborates with geological field observations, surface mapping and the results of previous investigations.

Detection of alteration zones using ASTER imagery and geological field observations: Al Wajh area, Northwestern Arabian Shield, Saudi Arabia

Neoproterozoic rocks are exposed in the southwestern Midyan terrane, which is located in the northwestern Arabian Shield. This terrane contains ophiolitic and metavolcanic rocks and arc-related intrusions. A NW-trending sinistral fault system (Najd Fault System, NFS) affected these Neoproterozoic rocks. The integration of remote sensing techniques, such as band combinations and band ratios of ASTER images, with field observations, helped to discriminate sulfide-rich rocks and to delineate alteration zones, gossans, and quartz veins, which commonly host ore mineralization. The band ratios used were the Al-OH minerals/advanced argillic alteration and the silica and Fe2+ band ratios. ASTER images were used to discriminate different rock units and construct an alteration map of the study area. Additionally, principal component analysis and frequency filtering techniques for ASTER images were used to extract linear faults and shear zone structures. Remote sensing ASTER images helped in the discovery of ancient mines that had not been previously recorded in the study area.